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RISHON LE-ZION, Israel A proprietary packaging method allows temperature-sensitive components such as memory ICs and relays to be surface mounted using reflow soldering despite being sensitive to exposure to high temperatures for long periods. The patented process, created by Cellergy Ltd., can also be applied to components that were compatible with tin/lead-based reflow soldering processes reaching peak temperatures of 235° or 240°C, but could not withstand 250°C peaks required for lead-free processes.
Cellergy's method is based on a double-layer phenomenon that occurs between a conductive solid and a liquid interface. Charge separation in the interface causes capacitance. Electronic charge then collects on the solid electrode and counter charge in the form of ionic charge forms in the liquid. To achieve this, an aqueous electrolyte that does not decompose at high temperatures is teamed with a thin shell to create a convective thermal resistance between the shell and the surrounding air of the reflow oven.
The process includes a fabric in the gap fill that soaks up deionized water during vapor diffusion when temperatures near 100°C. This allows the reflow soldering of temperature-sensitive and lead-free components. Cellergy developed the product for its electrochemical double-layer capacitors (EDCL), and is applying it to their supercapacitor line for portable electronic applications.